The electronic control unit in the electric power steering device equipped in a vehicle controls driving of the electric motor, and includes a power board or a power module equipped with switching elements, and a control board on which a control device of controlling an output current from the power module is implemented. The power module is electrically connected with the electric motor via an output connector, and the control board is electrically connected with the battery and the torque sensor of the vehicle.
In this situation, there is a demand for downsizing the ECU and the electric motor to be flexibly applied to arranged positions in a vehicle depending on the type of the vehicle. To address this demand, the electric power steering device in which the electronic control unit and the electric motor are integrated, as disclosed in Patent Literature 1 is conventionally proposed.
The ECU of the electric power steering device of Patent Literature 1 includes a power board on which switching elements are mounted, a control module that controls output currents from the power board, a DC conductor module including a power terminal block to which the power is supplied from the battery, and an AC conductor module including a motor terminal block that supplies the power to the electric motor.
Then, the power board is screwed onto a metal housing, and in addition, the DC conductor module and the AC conductor module are arranged above the power board, and are respectively screwed onto the metal housing. Also, the control module is arranged above the DC conductor module and the AC conductor module, and is screwed onto the metal housing.
Here, discrete parts that are considered to electronic parts short in height, such as switching elements or shunt resistances, and discrete parts that are considered to electronic parts tall in height, such as relays or jumper leads are mounted on the power board. On the other hand, discrete parts that are considered to be electronic parts having large sizes and tall heights such as electrolytic capacitors, relays, and normal filters are mounted on the bottom face of the bus bar of the DC conductor module arranged to face the power board vertically. In order to reduce the height of the ECU, the power board and the DC conductor module are arranged so that the afore-mentioned discrete parts tall in height do not interfere with each other.